Coyote ambient temp sensor wiring question

[Fordman114]

Just put the Coyote in my MK4 for the first time. I am adjusting the wiring harnesses trying to route everything. I have a question about the ambient air temperature sensor location. Should that be located outside the engine bay? That would be my thought so that it doesn't sense the superheated engine bay temperature or is it the temperature near the air intake tube that they want to sample?

[Andrew Davis]

fordman114,
had the same question, all I found was in the mustang it was an instrument (thermistor?) located in the grill to provide the current ambient temp. Like an OAT on aircraft. Not sure how critical it is to the ECU.

[edwardb]

I'm not remotely an expert on this subject. But several comments/observations:

- On the crate version of the Gen 3 Coyote (you don't say if yours is the crate version with control pack, so not sure if this applies) there is a harness connection marked C132 Ambient Air Temp but nothing to plug into it. For my Gen 3 Coyote build of a couple years ago, I tied that leg of the harness out of the way and haven't detected any issues. Coupe is done and in its third driving season. Several others have asked the same question about this unused connection and also left it unplugged or removed it.

- On a Mustang, there is an ambient temperature sensor external to the engine (somewhere on the front in the area of the radiator) that is apparently for the outside air temp display on the dash plus the PCM uses it to influence how the A/C operates. Plus maybe more but I just don't know. But not mentioned in either the Ford Performance or Factory Five instructions. Since our cars don't have the temp display, and the aftermarket A/C system (I have it in my Coupe) isn't connected to the PCM in any way, doesn't seem applicable to our builds.

- If you scan the ODB2 port with live data, there is an intake air temp reading. Seems to be the under hood temp based on what I'm seeing, which makes sense. So the PCM is getting an air temp signal. Obviously from another sensor somewhere. No idea where and don't know what the PCM does with it. But I expect it's factored into the tuning parameters somehow.

- Most Coyote installations, including mine, are drawing intake air from the engine compartment. On DD's, they do have the airbox drawing outside air and technically this is a better arrangement since it's typically cooler. I've seen some FF builds where guys have routed air from the outside, e.g. from the wheel well in a couple cases. No doubt gives a small bump in performance. But nothing I've pursued or needed for my driving.

[CraigS]

My experience on other brands is that intake air temp sensor is built into the air flow meter and that is what the pcm uses to adjust air/fuel mixture. Ambient air temp is out in the grill somewhere generally as far from the radiator as possible so heat soaking from the radiator while in traffic doesn't affect it. I agree w/ EdwardB that it runs the outside temp display and probably affects the AC operation. It may also pop up a message that roads may be slippery or similar. For your FFR, I'd probably tape it to the harness where ever it is most convenient to hide it.

[Fordman114]

I bought an AAT sensor for less that $20, but after reading the posts I think you guys are right and it isn't used by the PCM. I'll bury it in the harness.

Thanks for your input

[klawrence]

yeah I bought an AAT for my Gen3 in the coupe and mounted well because it was there. The IAT (intake air temp) is read from the MAF on the coyote. On my F100 with GEN1 coyote supercharged, had to bypass the IAT in the MAF and place is post Supercharger...as that air could be a touch warmer after being compressed.